Epinephrine-containing neurons are located in an area of the brain of strategic importance for the regulation of blood pressure. Although no direct rate for these cells has been established, it was of interest that while control animals possessed about 700 adrenergic cells per brain the stroke-prone SHR contained about 900 cells per brain (last year). More recently we have observed that unilateral carotid legation below the bifurcation results in a significant increase in phenylthanolamine-N-methyl transferase (PNMT) activity in the contrulateral C1 and C2 regions of the brainstem. Since most nerves transmitting baroreceptor information cross the midline, it is concluded that the reduction in blood pressure and the flow beyond the legation is causing an increase in the activity of epinephrine neurons as indexed by the enzyme PNMT. This provides circumstantial evidence that these neurons are involved in the baroreflex.